A conveyor-band filter apparatus of this type is already known from patent specification EP 0 291 574 B1. Conveyor-band filter apparatuses of this type, so-called Paternoster filter rakes, serve primarily for the mechanical cleansing of flowing sewage in corresponding conduits, the mount lower part of the frame mount, mostly arranged at an inclination during operation, being introduced into a conduit of this kind. The sewage flows through the filter elements which discharge the filtered material, incapable of passing through the filter screens, out of the conduit via the mount upper part. The filter elements are designed differently, according to the particular intended use, in terms of the type, extent and distribution of the throughflow orifices; alternating arrangements have proved especially expedient.
However, considerable difficulties in filtering out sewage by means of such a known conveyor-band filter apparatus arise when the material to be filtered out has mixed in it relatively coarse solid fragments, such as stones, pieces of wood or the like, which slide off from the filter elements conveying the filtered material and fall back into the conduit or which cannot even be picked up at all. They remain in the conduit and impede the mechanical cleansing to an increasing extent, so that they constantly have to be removed by means of appropriate aids. A continuous mode of operation of the conveyor-band filter apparatus is no longer guaranteed in the case of sewage laden in this way; stoppage times and a high labor outlay are the inevitable consequences.
A filter apparatus having filter elements fastened to a rotating chain drive is known from DE-A-4 200 366. These filter elements are each pivotably fastened at one end to the chain drive and in each case rest with their other end against one another, so that, in the deflecting region, the filter elements are pivotable relative to one another and relative to the chain drive. The ends of these sheet-like filter elements are made comb-shaped and are angularly bent.
The object of the invention is, therefore, to provide a conveyor-band filter apparatus of the type initially designated in more detail, in such a way that the filtration of flowing liquids contaminated with solids is not impeded by coarse solid fragments carried along with the liquids or deposited so as to rest in the conduit and, during the operating of the conveyor-band filter apparatus, these solid fragments are constantly discharged together with the remaining fine-grained filtered material.